it does not increase the mass. like how oxygen doesn't increase the mass of animals
That's right. It reduces our mass, by "burning" the sugar.
You breathe in oxygen, you breath out carbon dioxide. What do you think is going to happen?
the carbondioxide or oxygen doesn't increase the mass of trees.
The carbon dioxide does increase the mass of a tree. If you put a tree in a carbon dioxide free environment, it cannot grow.
Prove photosynthesis.
It has been proven beyond any reasonable doubt.
One example was by placing a mouse and plant in a bell jar. (compared with just a mouse)
The mouse lived with the plant, as the plant produced oxygen for the mouse to use for respiration. (they even did it with a human, but not the control).
Without the plants, they don't get oxygen and they die.
The other key bit of proof is that plants need light to grow.
There is no laboratuary experiment prove the photosentesis.
You ignoring them doesn't mean they don't exist.
Here is a nice simple experiment for you:
Get an oxygen sensor and carbon dioxide sensor.
Place them in a sealed (airtight) container with a plant.
See what happens when there is no light given to the plant.
See what happens (as an extra control) when you illuminate various regions of the container, without illuminating the plant.
Then see what happens when you illuminate the plant (sunlight works best but other growing lights work as well, as should generic incandescent light globes).
In all cases ensure the plant has plenty of water (but not so much that you kill it with it) as well as decent soil with nutrients.
(as an added test, add extra carbon dioxide to the container first so it doesn't run out)
If you do this, guess what the results will be?
The case of the non-illuminated plants, the oxygen will be consumed and CO2 will be produced.
In the case of the illuminated plant, the opposite will happen (assuming it has enough light, and there is enough CO2).
That experiment doesn't prove the photosentesis.
Yes it does.
Because the closed tube doesn't have carbondioxide but doesn'T have oxygen too.
No. It has oxygen. The potassium hydroxide absorbs the CO2 to form potassium carbonate. It doesn't absorb the oxygen.
If you like you can do a more complicated experiment, by flowing air through a tube filled with potassium hydroxide (at a slow rate to ensure all the CO2 is gone), or by feeding it with an oxygen/nitrogen mix which has no CO2.
You can also try a simple control of not putting in the potassium hydroxide and see what happens.
Or you can show it needs the light by having a leaf covered up but still exposed to the air.